Neoadjuvant chemotherapy is indicated in locally advanced breast cancer and is the standard option for patients with operable breast cancer, who are not candidates for breast-conserving surgery. To minimize adverse effects of neoadjuvant chemotherapy on breast cancer patients, non-responders must be identified as early as possible. Current methods to assess early response (clinical examination, ultrasound, MRI, mammography) correlate poorly with tumor response at the end of the treatment. Functional imaging using Positron Emission Tomography was shown to be useful in prediction of pathological response after two cycles of chemotherapy, but it is expensive and of limited availability. Preliminary investigations have shown that tissue parameters measurable by near infrared spectroscopy (hemoglobin, water and lipids) exhibit changes early in the treatment period that appear to correlate with final pathological outcome. Additionally, subjecting breast tissue to mild compression and measuring the transient changes in the concentration of hemoglobin species was shown to permit the estimation of tissue metabolic parameters, such as specific blood flow (BF) and oxygen consumption (OC) that relate to tumor physiology on a more fundamental level. Two key requirements for estimating OC and BF are high data acquisition rate (at least 1 Hz) and high accuracy in the measurement of hemoglobin species concentration (achievable by multi-wavelength imaging). There is an urgent need for both novel imaging technologies and new methods of evaluation that could have a significant positive impact on breast cancer treatment using primary chemotherapy. The innovation of this program is the development of an accurate and fast multi-spectral optical imaging system that utilizes these recent research methods with mild compression. We will expand our existing CW6 optical imaging system, by doubling the sources to 64 lasers. We will also integrate a Frequency Domain System with RF modulation at 70 MHz, providing baseline and absolute measurements. The complete system will provide 6 wavelengths for imaging for accurate measurement of the major tissue chromophores, while maintaining frame rates well over 1 Hz. Dynamic phantoms will be used for system characterization, while initial breast imaging data will be obtained by recruiting and testing healthy volunteers. Successful completion of the proposed work is expected to lead to a Phase II SBIR pilot study of breast neoadjuvant chemotherapy monitoring at the Massachusetts General Hospital and University of California at Irvine cancer centers. [unreadable] [unreadable] [unreadable]